Protective gap for electrical equipment



Nov. 29, 1932. R. B. ASHBROOK ET AL 1,889,086

I PROTECTIVE GAP FOR ELECTRICAL EQUIPMENT Filed Dec. 5o, 1929 777,60 rfaf/Yff l /a @fw PatentedA Nov. 29, 1932 UNITI-:D STATES PATENT'oFrIcE;

i lsaeae ROY n. AsHBnoox, or SAN GABRIEL, MABEL IvIAoFIEImAN, or ALHAMBRA., :eoY lEDWIN enansmaom, or Irrennwoen, aan BENJAMIN r. pancarta, or nos Attentes, CALI.

FORNIA PROTECTIVE GAI ron ELEernICAI; EQUIPMENT Application filed December 30, 1929. v Serial No. 417,468.

rIhis invention has to do with an arrester or protective gap for electrical equipment,and is an object of the invention to provide a j device of this character which is etlicient and dependable in low voltage lines and capable of handling high currents over comparative ly long periods of time.

In various fields of electrical development v there is need for an arrester thatwill operate w at relatively low voltages and yet have high current carrying capacity over` comparatively long periods of time. -The situations in which such devices may be used further require uniform voltage break down and'ability to properly clear the circuit after operation. Arresters such as we refer to are needed particularly in connection with telephone lines, and the like, which are subject to highV between-wire-voltages and high voltage to ground. In lines or circuits of this type where continuity of service is essential, it is not satisfactory to protect the equipment or instruments by fuses which disconnect or open the circuit until a new fuse is installed. Y Arresters that are on the market available for use and capable of functioning properly on low voltages will carry or'Q amperes for only a second or two. A longer application of such amperage destroys the arrester. lt is an object of the present invention to provide an arrester suitable for use in low voltage circuits and capable of effectively and dependably handling high currents over coma5 para'ively long periods of time. An embodiment of the invention which has been sucf cess-fully operated, protects ajlow voltagel telephone circuit and will carry 2O to 25 amperes for a period of l2 to 15 minutes without breaking down or being damaged..`

Another object of the present invention is to provide a construction for a gap arrester whereby heat generated by arcing in the arrester is rapidly and effectively removed from the points of arcing in a manner to prevent overheating of the tips of the electrodes.

Another object of the invention is to provide a combination of materials in a gap arrester which provides a practical, eiticient and inexpensive device that will handle an are dependably over a longfperiod of time without the electrodes being damaged.`

A further object of the invention is to pro= vide a gap arrester having electrodes with fiat polished faces over which an arc will spread rather than concentrate at one pointy Another object of the invention-is to' provide a gap arrester having electrodes with flat polished faces without edges or. joints at which an are will concentrate.` l

The various objects and features of our invention will be best andmore fully understood from the .following detailed description of a typical yforni and application of the invention, throughout which description we refer .to the accompanying` drawing, ,in-

Fig. l is anV exterior elevationvv of thegap 'V Fig. 2 is a detailed transversesectional view of the arrester being a view tak-en as indicated by line -2-2 on Fig. 1. ,'Fig. 3 is a longitudinal detailed sectional View through ione of the electrodes'f the yarrester being a view taken as indicated by line 3 8,011 Fig. 2, and Fig. dis a detailed transverse sectional View taken as indicated by line 4 4 on Fig. l.

The present invention provides 'an' arrester useful in various circuits and .intended particularly to handle low voltage circuits and yet be capable of carrying a comparatively high amperage over a substantial period of time. A telephone line subject to high between-wire-,voltage and high voltageto-ground presents a typical situation inl between their tips. In the drawing we have shown a mountingfor the electrodes includ-` ing a support or frame 10 of suitable insulating material having spaced abutinents 11, a

spacer 12 between the inner or adjoining ends y of the electrodes, and springs 18 at the outer lends of the electrodes and engaging the abut- Vments'11of the frame zto lholdorurge the electrodes inwardly so that' thev spacer is clamped between them. Y

`The present `invention resides primarily in the electrodes, and as both electrodes may be the same, We will proceed with af detailed description of a single electrode, it beingunderstood that such description may *apply*v to both. n Y Y The electrode provided by the invention includes, generally, a corel llfforiiied of a material which is a good electrical conductor andalso a good heat conductor,a tiprl on the inner orvgap end of the `core forming a flat, 'smooth gap face yof considerable area `and formed of material which is a good electrical conductor and which is not readily impaired or injuredv by heat, land a body 16 in connection Withthe core and formed of'material causing it to act as areceiver or absorbing element for the heat conducted by the core.

The core lll maybe in the form [of an elongated member or bar having one eno suit- .ablerfor carrying the tip' 15a-iid having a part adapted to receivefthebody v In the y preferred forni of the invention illustrated the core let is in the nature of a bar round in` cross section and sufficiently long to have a large direct bearing engagement With the body V16, as-,Will be hereinafter described. The invention provides that the corebe formed ofmat'erial which is a-'good electrical conductor and vat the saine'tiine capable of ra idl conducting heat. lInA ractice We C: i

have found it advantageous to form the core of copper assiich material 'is lan excellent n electrical conductor and has a hioh heat conductivity. f 1

The facing or tip laprovided onthe inner or gap end of the core 'is preferably applied or formed directly on the end of the core and is formed of a material which vrillnot melt or break dovvn-under'the arcing ,conditions surface?7 ive'inean a finely finished plane surface such asV a polishedplane surface, as distinguished:` from a and from a surface that is i icre or less granular or hascrackssea-ins or ioints in it. In other Words the lsurface is made to possess such degrees of firmness and smoothness that thejarc instead of'centering or concentrating sur-face of ordinary finish 12, may be guided by suitable projections 26 Von theV outer ends of the bodies 16 of the elec- ,Y

at one or more points spreads more or less uniformly over the entire surface. Silver not only eflectivelyresists heat but also has a high heat conductivity, and therefore heat generated by arcing at the face 17 is effectively transmitted orccnducted through the tip to the core. Thetipl is formedsothat its Y face isffree of cracks or joints and so that it has no edges at ywhich ar'cin'gwill concentrate. In practicetlie margin lor edge portion of the face is rounded vor `beveled as shown in the` drawing.

The body 16, provided for absorbing or rev ceiving the heat from the core may be a com# paratively large element or block carried directly on the core to have a long bearing contactvith the core.` In'theconstruction illus- 1 tratedtlie body 16 is in the formof a'large block of material havingk an `opening20 through it accurately receiving the core 14.

Thevbody 16 .is split at 21and provided 4With clamp bolts 22 .vhiclifinay be" operated to tighten theV cody onto `-tlie`l corev to assure a tight bearing engagement between j the'core and body. In practice one of the bolts 22inay be extended for use as a terminal or binding post vforth-eelectrode, as shown in the drawing. In practiceive have found lit advantageoiis`V to form the bodylG of cast iion as suchinaterial has a .high heat storagev capac-` Aityand will readily receive heat from the core 14C inthe desired manner. Further, v,cast Y iron isa material which Vis inexpensive and ivhich can beadvantageously Vfinished or inachi ned in the manner above described. Y The spacer 12, which We have shown as interposed between the inner ends of the electi'odes to space the electrodes so that thereis the vdesired gap between their tips, may bean annularbody or ring of insulating material. In the construction illustrated annular projections 25 are provided on the inner ends of fies the bodies ofthe electrodes tofit intothe insulatiiig ring orfspacer12 to properlyr guide the spacer Witlireference to the electrodes, as clearly illustratediin Figs. 1Y and 2 of the drawing. By .making thespacer r12 of the desired Width orl length, itoperates to space the electrodes so that the faces 17 of the electrode tips are yparallel and the desired disltance apart.. yThe ends or bearing faces of thev spacer are ground so that they are truly parallel and thus space the electrodes With their faces in trueparallelism." It Will be obvious that the flat smooth` faces' 17, being thus artrodes and inay be held in suitable recesses 27 Vprovided in the abutinents 11 of the frame.

The construction Which We havendescribed iio 'Y' iis f ranged parallel With each other, form a'uni-`V lmounting` arrangement.

noted th at the construction is simple and inexpensive of manufacture andV it will be obvious that it is capable of considerable modification or variation to suit varying conditions.

-, Under actual operating conditions anarc occurring between the faces I7 is spread and does not concentrate at any one spot. The invention thus distinguishes over constructions in which the electrode faces have cracks or joints in them or have'sharp edges. -Further, by using polished silver faces we elimi` nate pitting of the gap faces such as occurs with the use of certain materials, for example, carbon. The storing or absorbing body being in direct contact with the conductive core causes the heat to be handled so that the gap operates dependably and effectively.

-laving described only a typical preferred form of our invention, we donot wish to limit ourselves to the specific detailsset forth, but wish to reserve to ourselves any changes or variations that may appear to those skilled in the art or fall within the scope of the following claims.

Having described our invention, we claim:

l. A protective gap for use in connection with an electric circuit including, an electrode having a core of high heat conducting capacity and having a flat polish silver gap face, and a metal body o-f large volume relative to the core and of high heat absorbing capacity directly engaged around the core.

2. A protective gap for use in connection with an electric circuit including, an electrode having a core of high heat conducting capacity, a silver tip on the core having a flat smooth polished gap face, and a metal body of high heat absorbing capacity in direct connection with the core.

3. A protective gap for use in connection with an electric circuit including, an electrode having a core of high heat conducting capacity, a tip of silver on the core presenting a flat smooth polished gap face, and a large metal body of high heat absorbing capacity in direct connection with the core,

4. A protective gap for use in connection with an electric circuitl including, an electrode having a copper core, a silver tip on the core having a flat polished gap face, and an'iron body engaged around the core, the body being of substantial bulk with respect to the core and having a large direct bearing engagement with the core. f

5. A protective Krap for use in connectionv with an electric circuit including, two electrodes each including acopper core, an iron body, the body being split and engaged direct-l ly around the core, and a screw member operating to clamp the body on the core and forming a terminal for making electric con- `nection with'the electrode, and silver tips'on the vcores having flat polished parallel gap faces.

6. A protective gap for use in connection with an electric circuit including, two electrodes each having a core and a heat absorbing vmetal body Surrounding the core and in direct engagement'therewith, silver tips on the electrodes having spaced parallel polishing gap faces, and a spacer of insulating materia-l between the electrodes, the spacer being in engagement with vthe said bodies of the electrodes, the ends of the spacer being perfectly parallel and accurately fitting against the electrodes to maintain the gap facer in perfect parallelism.

7 A .protective gap for use in connection with an electric circuit including, two elec-` Y trodes each having a core and a heat absorb.l i

ing metal body of large volume relative to the core surrounding the core and having direct engagement with the core, silver tips on the cores havirig parallel polished flat gap*V faces, and a spacer ring of insulating material between the electrodes the spacer being in engagement with the said bodies of the electrodes, the bodies of the electrodes having parts projecting into the ring.y

8. A protective gap for use` in an electric circuit including, two velectrodes having' 10. A protectivegap for use in anelectric circuit including, two spaced cores of heat conducting material, silver tips on the adjoining ends ofthe cores,the faces of the tips l being parallel polished smooth and flat, and

comparatively large heat absorbing bodies y directly connected with the cores. n

In witness that we claim the foregoing we have hereunto subscribed our names thi-s 20th day of December, 1929.

ROY B. ASHBROOK. MABEL MAGFERRAN. i ROY EDWIN QUANSTROM. BENJAMIN F. DENGLER. 

